Torsional snap action device



March 18, 1941. Q Q VAN DUSEN, JR 2,235,779

TORSIONAL SNAP ACTION DEVICE Filed March 8, 1959 ,fimaenfor 7 George C. Van Dusen Jr.

Patented Mar. 18, 1941 i 2,235,779

UNITED STATES PATENT OFFICE 2,235,779 'ronslormi. SNAP ACTION DEVICE George C. Van Dusen, Jr., St. Louis Park, Minn, assignor' to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Application March 8, 1939, Serial No. 260,605

17 Claims, (Cl. 200-138) The present invention relates to a snap action and 23 and thus place a tensional stress in the device and more particularly to a device which arms 22 and 23 and the shankportion 2| of the snaps from one position to another due to tormember 20. The purpose of setting up this stress sional stress. in the aforesaid members will be more fully de- An object of my invention is to provide a snap scribed in the operation of the device. The block action device of simple structure comprising few 30 is secured to a U-shaped bracket 3| by screws parts, but being accurate and positive in opera- 32. The bracket 3| is in turn secured to the base tion. plate I*by screws 33.

Another, more specific object, is to provide a Conventionally secured on the top of the snap action device which requires no external bracket 3| are two insulating electrical terminal springs, bails, or stops to prevent overtravel blocks 35 and 35. Secured to the terminal blocks thereof. 35 and 36 are the contact brackets 31 and 38, re-

Another object is. to provide an electrical spectively, and a similar second set of contacts, switching mechanism, employing a novel double only one of which 3111 is shown. A contact bridge snap action to inhibit vanishing contact pressure, member 39 formed of conducting material carries l5 and which will be compact and simple in strucmovable contacts 40 and 4| which cooperate with ture. V the stationary contacts on the brackets 31 and 38 A further object is to provide a snap action as well as the contacts on the similar brackets.

mechanism which operates between a plurality of l The upper part 'of the bracket 3| is provided positions of equilibrium that are determined with an hole 45 and a pair of recesses 46 into solely by stresses set up in the snapping member. which the legs 41 of the carrying member 48 for Other objects will become apparent by referthe bridge 39 are adapted to seat. The member ence to the accompanying specification, the 41 is provided with an hole 50 into which one end claims, and the drawing, in which of the spring 5| is hooked. The opposite end of Figure 1 is an elevational view of a form f the spring 5| is hooked through the hole 52 in my invention with certain parts in section, the ear 6 p the pp member There- Figure 2 is a sectional view taken on the line fore it is seen thatthe snapp member is 22 of Figure 1 with certain parts in l ti n operatively connected to the electrical contact and another part represented by broken lines mechanism in a manner to provide an overcento more clearly illustrate the principle of the ter snap action to the contact bridge 39 in makdevice, and ing and breaking the electrical circuit, as is Figure 3 is a fragmentary'view of a modificaclearly ShOW in Figure 2.

tion. Referring now to Figure 3, a snapping mem- In Figures 1 and 2, a base plate III is provided her I20 is shown secured to the enlarged portion -which is adapted to be secured to an air duct, W of the rod The pp member i5 5 bonnet of a furnace, or the like, by means f provided with arms I22 and I23. The upper arm screws which can be placed throu h hol IL is provided with a finger I24 similar to the finger The base plate I0 is also provided with an ll 24 of Figures 1 and 2. The lower arm I23 is drawn support I2, the end of which is provided provided with a block I secured to the arm with an ear I3 to which a bimetal helix u is se- I23 by means of rivets The block I40 0 cured by a screw IS. The free end of th biries a set screw I42 which is adapted to coopermetal I4 is secured to a rod I6 by a, screw |1 ate with the lower recess 29 of the block 30. The opposite end of the rod I6 h s an enlarged Therefore it is seen that means are provided to portion I8 to which a snapping element 20 is seadjust the amount of tensional Spreading cured by rivets I9 or other conventional means. Stress placed in the pp member 121 The snapping element 2|! is provided with a shank portion 2| which is bifurcated to form two. arms 22 and 23. The two arms 22 and 23 are Referring to Figure 2, the snapping member inturned to form fingers 24 and 25, respectively. 20 is shown in the position a sumed w pp The arm 22 is also provided with an ear 2, th in a clockwise direction. The device has two popurpose of which will be.hereinafter more fully sitions. of equilibrium, a counter-clockwise posie i' tion and a clockwise position. These positions of The fingers 24 and 25 a.r'e adapted to engage equilibrium are assumed when the tensional stress recesses. 23 and 29 in a. block. The block in the snapping member 20 is equalized by the tor- Operation i l-is of a size suftlcient to spread the arms 22 sional stress set up in.the arms 22 and 23 as they are warped in planes oblique to the plane common to the member 28 due to the rotation of the fingers 24 and 25 about their respective recesses 28 and 29 in the blockSli. Because the fingers 24 and 25 rotate about independent pivot points the tendency of the arms 22 and 23 is to approach each other as they are rotated away from the vertical dead center position. Inasmuch as the initial stress placed in the snapping member 20 is reduced as the member is rotated and the torsional stress placed in the arms 22 and 23 is increased because of that rotation, a position of equilibrium of stresses will be reached at a point predetermined by the initial spreading stress placed in the member 20.

The positions of balance of the member 20 in which the device will stop after being snapped over a dead center mid position'will be determined by the amount of initial spreading tension placed in the snapping member 28. In that form of my invention shown in Figures 1 and 2 this tension may be predetermined by means of different sized blocks 30. In Figure 3 the set screw M2 is adapted to adjust the initial tension in the snapping element I20.

- Assuming the parts in the position shown and the bimetallic helix i4 being subjected to a change in temperature and rotating the rod IS: the snapping member 20 will be rotated in a counterclockwise direction. When the member 20 is thus rotated, it will be seen that the torsional stress in the arms 22 and 23 will decrease because they will be returned to the common plane of the member 20. The spreading stress in the member 20 will be increasing because the fingers rotating around their respective bearing points will be spreading the arms 22 and 23. The member 20 will be rotated to a substantially vertical position past dead center at which time the torsional stress caused by convergence of the arms 22 and 23 will create a couple which will rotate the member 20 in cooperation with the bimetallic helix I4.

Therefore, it is seen that the device after passing a dead center mid position will reach a point when the stress within the snapping member 20 will cooperate with the stress in the bimetallic member I4, at which time the device will snap into a position of counter-clockwise equilibrium.

When the snapping element 2|) is snapped past center position the connecting spring which is hooked to the contact carrying member 41 will be moved past the dead center position in alignment with the recesses 46. Therefore after the snapping member 20 has snapped into an extreme position the contact carrying member will snap from one set of stationary contacts to the other. Because the contact carrying member does not move away from the contacts until the snapping 'member 20 has snapped past the dead center position vanishing contact pressure is inhibited between the closed contacts.

While I have shown my device in connection with a temperature responsive element it will be understood that this snap acting mechanism could be used with humidity responsive devices, pressure responsive devices, or as a manual overcenter switch. It is also fully anticipated that similar devices could be constructed wherein the snapping member is placed under a compressional stress, rather than tensional stress as utilized, without departing ffiim the spirit of the present invention. Many modifications and forms of my invention will occur to those skilled in the art, therefore it should be clearly understood that I am not to be limited in y nv tion only to those forms-shown and described but by the scope of the appended claims.

I claim as my invention:

1. A snap action switching mechanism comprising in combination, a member providing a pair of opposed bearing surfaces, a resilient member provided with a pair of fingers, said fingers being in engagement with said bearing surfaces so as to place stress in said resilient member, means for causing relative rotation between said bearing surfaces and said resilient member whereby said mechanism snaps from one position to another, and switching means operated by one of said members.

2. A snap action control mechanism, in combination,a member providing a pair of opposed surfaces, a resilient member provided with a pair of fingers having forcible and rotative engagement with said surfaces, said forcible engagement setting up a stress in said resilient member, means for providing relative rotative movement between said surfaces and said fingers whereby the stress in said resilient member is varied and a snap action is produced, and control means operated by one of said members.

3. A snap action mechanism comprising, a resilient member provided with a pair of spaced fingers, a pair of opposed spaced bearings cooperating with said spaced fingers to set up a stress in said resilient member, means to rotate said resilient member to cause rotation of said fingers about the respective bearing of each to vary the stress in said resilient member whereby said member snaps from one position to another.

4. A snap action control mechanism comprising, a bifurcated member of resilient material provided with a pair of spaced fingers, a pair of opposed spaced bearings which cooperate with said fingers to place stress in said resilient member, means to rotate said resilient member to cause rotation of said fingers about the respective bearing of each to vary the stress in said resilient member whereby said member snaps from one position to another, and control means operated by said member.

5. A snap action switching mechanism comprising, a resilient memberprovided with a pair of spaced fingers, a pair of opposed spaced bearings cooperating with said, spaced fingers to set up a stress in said resilient member, means to rotate said resilient member to cause rotation of said fingers about the respective bearing of each to vary the stress in said resilient member whereopposed spaced bearings which cooperate with said fingers to place stress in said resilient member, means to rotate said resilient member to cause rotation of said fingers about the respective bearing of each to vary the stress in said resilient member whereby said member snaps from one position to another, a rotative member provided with electrical contacts, bearing means about which said contact member rotates, fixed electrical contacts in cooperable relation with said first contacts, and connecting means between said rotative member and said resilient member whereby said contacts move into and out of engagement with a snap action subsequent to the snap action of said resilient member.

'7. A snap action mechanism comprising a resilient member, said member being bifurcated to form a pair of spaced arms normally in the same plane, means to stress said arms in opposite directions transverse to said bifurcation, and means to cause relative rotation between said stressing means and'said resilient member about an axis substantially longitudinally of said bifurcation.

8. A snap action mechanism comprising, a resilient member, said member being bifurcated to form a pair of spaced arms normally in the same plane, means stressing said arms in opposite directions transverse to said bifurcation, which stress tends to warp said arms into substantially parallel planes that are oblique to the common plane, and means to cause relative rotation between said stressing means and said resilient member about an axis substantially longitudinally of said bifurcation.

9. A snap action mechanism comprising, a resilient member, said member being bifurcated to form a pair of spaced arms normally in the same plane, means placing a stress in said arms, which stress tends to move said member in either direction from a dead center position, said arms when moved by said stress cooperating with said stressing means to create a counteracting stress in said resilient member, said first mentioned stress decreasing and said second mentioned stress increasing as said member is moved' from a dead center position, and means to cause relative rotation between said stressing means and said resilient member about an axis substantially longitudinally of said bifurcation.

10. A snap action mechanism comprising, a resilient member, said member being bifurcated to form a pair of spaced arms normally in the same plane, means stressing said arms in opposite directions thereby tending to move them to one of two positions of stability of resiliency of Said member, and means to cause relative rotation between said stressing means of said resilient member about an axis substantially longitudinally said bifurcation.

11. A snap action mechanism comprising, a re silient member, said member being bifurcated to form a pair of spaced arms normally in the same plane, means stressing said arms in opposite directions transverse to said bifurcation, which stress tends to move said member from dead center position to one of two positions, said arms and said stressing means cooperating with said member to create a counteracting stress in said member when said arms and member are moved, said first mentioned stress increasing and said second mentioned stress decreasing as said member is moved from dead center position, and

means to cause relative rotation between said stressing means and said resilient member about an axis substantially longitudinally said bifurcation.

12. A snap action mechanism comprising, a resilient member, said member being bifurcated to form a pair of spaced arms normally in the same plane, stressing means to stress said arms in oppbsite directions transverse to said bifurcation, mean to cause relative rotation between said stressing means and said resilient member about an axis substantially longitudinally of said bifurcation, control means operated by one of said arms, and means to adjust the stress in said arms to change the control point of said control means.

. l 13. A snap action mechanism comprising, a resilient member, said member being bifurcated to form a pair of spaced arms normally in the same plane, stressing means to stress said arms in opposite directions thereby tending to move them to one of two positions of stability of resiliency of said member, means to cause relative rotation between said stressing means and said resilient member about an axis substantially longitudinally said bifurcation, control means operated by one of said arms, and means to adjust the stress in said arms to change the control point of said control means.

14. A snap action mechanism comprising, in combination, a member of resilient material provided with a pair of arms, a block provided with hearing recesses on opposite faces, said arms being in engagement with said recesses so as to place stress in said resilient member, means to rotate said member about an axis substantially longitudinally said arms, said rotation tending to vary the stress in said member to cause the mechanism to snap from one position to another, and means to manually adjust the stress in said arms.

15. A snap action mechanism comprising, a pair of members normally in a common plane, said members being biased for movement toward each other, means resisting said bias thereby causing said members to twist and to lie in substantially parallel different planes, and means for producing relative rotation between said bias resisting means and said "members.

16. A snap action mechanism comprising, a pair of members biased toward each other, means resisting relative movement of said members toward each other for causing said members to twist, and means to rotate said members in the same angular direction about said resisting means to thereby produce a snap action.

17. A snap action mechanism comprising, a pair of members biased toward each other, means resisting relative movement of said members toward each other for causing said members to twist, and means for producing relative rotation between said first means and said members causing said members to rotate in the same angular direction to thereby produce a snap action.

GEORGE C. VAN DUSEN, JR. 

